The progress that has been made in recent years in brain science has led to various studies on the relationship between human thought or behavior and brain activity. Attention is being focused on Brain-Machine Interface (BMI) technology for controlling external equipment or conveying one's intention to another person by noting a biosignal of, e.g., brain activity.
For example, neuromarketing is the study for investigating the brain activity related to consumer behavior using a functional MRI (fMRI) device or the like. A study is known in which, based on a brain activity measurement experiment using a fMRI apparatus, brain areas related to preferences or brand awareness were identified and brain activity differences were investigated (see Non Patent Literature 1).
The present inventor has shown, using a measurement technique involving extracellular recording of the action potential of a single neuron via electrodes placed in an animal brain, and by a simulation of neuronal ensemble activity, that the representation of relationships among a plurality of external stimuli (experimental conditions) in the brain can be estimated in terms of low-dimensional spatial information (see Non Patent Literature 2). However, many aspects of brain activity are still unknown, and the measurement methods have limitations.
The present inventor has also proposed a virtual decision function, and shown a calculation method therefor (see Non Patent Literature 3). Non Patent Literature 3 describes a method for predicting an alternative behavior from a neural activity such as a single neural activity.
The present inventor has also proposed an intention conveyance assist apparatus and method for conveying an intention by brain activity analysis (see Patent Literatures 1 and 2). The technology according to Patent Literatures 1 and 2 assists, for example, the conveyance of an intention of a person with motor impairment having difficulty speaking or writing, or of a person with severe motor impairment having difficulty performing an input operation on various devices using hands or legs. Particularly, in the field of nursing care/welfare device development, people such as the elderly or the sick may be unable to perform a complex input operation, require training to learn an operation method, or even have difficulty learning. The technology according to Patent Literatures 1 and 2 has enabled direct transmission of an intention without requiring a special operation. Further, the apparatus according to Patent Literatures 1 and 2 has enabled patients with speech impediment or the elderly to convey their intentions regarding basic personal care or feelings to the helper in simpler manner.
The present inventor has proposed a technique for showing a map of information representations in the brain by brain wave analysis performed on general test subjects, including non-handicapped persons (see Patent Literature 3). The present inventor has also proposed an apparatus and method for ranking by brain wave analysis the objects to be investigated (see Patent Literature 4). According to the technology of Patent Literature 4, the ranking of the objects to be investigated enables ranking of information about brain activity including both conscious awareness and subconscious awareness, which can be effectively utilized for marketing study and the like.
A prior-art search has identified a proposal to characterize a neural functional state of a test subject by the steps of feeding a stimulus to the test subject and monitoring a brain wave reaction during a neural activity caused by the stimulus, and to compare the brain wave reaction with the results obtained from other test subjects or a group of test subjects, or with the results obtained from the same test subject under different conditions (see Patent Literature 5). Another technology has also been proposed whereby an environment change determination unit is provided to determine whether a test subject has been given a stimulus by a change deviating from steady state in the environment around the test subject, and, if it is determined that the stimulus has been given, an event-related potential corresponding to the stimulus is detected to calculate, based on a feature quantity obtained from the potential, a value indicating the degree of concentration of the test subject (see Patent Literature 6).